Electric discharge device having heat conserving shields and sleeve



y 1966 c. L. PETERSON 3,250,934

ELECTRIC DISCHARGE DEVICE HAVING HEAT CONSERVING SHIELDS AND SLEEVEFiled Nov. 22, 1963 2 Sheets-Sheet 1 CARL L. PETERSON I NVEN TOR.

AT RNEY May 10, 1966 C. L. PETERSON ELECTRIC DISCHARGE DEVICE HAVINGHEAT CONSERVING SHIELDS AND SLEEVE Filed NOV. 22, 1963 2 Sheets-Sheet 2I47 I48 I46 I52 I08 us" -I03 I04 J27 IoI H? -I05 I45 I06 I40 9 CARL IPETERSON INVENTOR.

AT NY United States Patent 3,250,934 ELECTRIC DISCHARGE DEVICE HAVINGHEAT CONSERVING SHIELDS AND SLEEVE Carl L. Peterson, Rockport, Mass,assignor to Sylvania Electric Products Inc., a corporation of DelawareFiled Nov. 22, 1963, Ser. No. 325,672 4 Claims. (Cl. 31317) Thisinvention relates to high pressure electric discharge devices andparticularly to discharge devices containing mercury, iodine and a metalwhich modifies the lamps emission color.

High pressure electric discharge devices containing mercury are wellknown to the art. Such devices have been modified by adding a halide,particularly iodine, to the arc tube fill together with a metal whichchanges the lamps emission.

Examples of the modifications are given in the copending application ofWaymouth et al., S.N. 209,974, filed July 16, 1962 entitled HighPressure Electric Discharge Device; Waymouth et al., S.N. 230,944, filedOctober 10, 1962, entitled Electric Discharge Device and Butler et al.,SN. 239,272, filed November 21, 1962, entitled Electric DischargeDevice, each of the several applications being assigned to the sameassignee as the instant invention.

The devices of the art containing mercury alone have had serioushandicaps because of their emission color. The typical mercury dischargeproduced light consisting of discrete, separate wavelengths, generallycalled lines. Almost all of the radiation was contained in the blueregion together with a line in the green and a line in the yellow. Hencewhen conventional mercury lamps illuminated red objects, particularlythose reflecting light only in the range of 6000 to 6800 A., the objectsappeared black.

Because of the addition of iodine and metals which change the lampsemission color, it'has been found that the temperature at which the arctube operates has to be raised. Without such elevation in temperature,the chiciency is not high and the emission color can be changed.

I have now discovered a means to elevate the temperature of the arc tubeand hence increase the efliciency of the lamp. According to myinvention, I form a heatentrapping chamber by surrounding the arc tubewith a transparent glass sleeve and supporting the bottom and top of thesleeve with reflective plates. The construction of the plates not onlyraises the temperature of the arc tube but also prevents breakage of thesleeve.

Accordingly, the primary object of my invention is increasing theefliciency and stabilizing the emission color of metal-halidecontaining, high pressure electric discharge devices.

A feature of my invention is mounting a cylindrical glass sleeve aboutthe arc tube and supporting the sleeve by reflective plates on tabsextending therefrom.

An advantage of my invention is that the support of the glass sleevewhich I obtain increases the stability of the device and reducesbreakage.

The many other objects, features and advantages of the instant inventionwill become manifest to those conversant with the art upon reading thefollowing specification when taken in conjunction with the accompanyingdrawings wherein preferred embodiments of my device for increasing theefliciency and stabilizing the emission color of mercury-halide-metalcontaining high pressure electric discharge devices are shown anddescribed by way of illustrative examples.

Of these drawings;

FIGURE 1 is an elevational view, partly in crosssection, of a highpressure electric discharge device showing one type of arc tube withwhich the device of my invention can be used.

3,250,934 Patented May 10, 1966 FIGURE 2 is an enlarged perspective viewtaken on line 2-2 of FIGURE 1 of the mounting of the arc tube on theupper reflective shield.

FIGURE 3 is an elevational view, partly in crosssection, of a highpressure electric discharge device showing another type of arc tube withwhich my invention applicability.

A high pressure discharge device such, as shown in FIGURE '1, comprisesan outer vitreous envelope or jacket 2 of generally tubular form havinga central bulbous portion 3. The jacket is provided at its lower endwith a re-entrant stem 10 having a press through which extend relativelystiff lead-in wires 6 and 7 connected at their outer ends to theelectrical contacts of a usual screwtype base 8 and at their inner endsto the arc tube and the harness.

The arc tube 12 is made of quartz and has sealed therein at oppositeends, the main discharge electrode 13 and 14, which are supported onlead-in wires 4 and 5 respectively. Each main electrode comprises a coreportion which may be a prolongation of the lead-in wires 4 and 5 and maybe prepared of a suitable refractory metal such as tungsten ormolybdenum. The prolongations of the lead-in wires 4 and 5 aresurrounded by tungsten wire helixes. A small piece or sliver of thoriummetal (not shown) is inserted between the core and the helix to reducethe cathode drop during operation. An auxiliary starting pro-be orelectrode 18 is provided at the base end of the arc tube 12 adjacentmain electrode 14 and comprises an inwardly projecting end of anotherlead-in wlre.

Each of the current lead-in wires described above have their ends weldedto intermediate foil sections of molybdenum which are hermeticallysealed within pinch seal portions of the quartz arc tube. The foilsections are very thin, for example approximately 0.0008" thick, and gointo tension without rupturing or scaling off when the quartz cools.Relatively short molybdenum wires 23, 24 and 25 are welded to the outerends of the foil and serve to convey current to the various electrodesinside the arc tube 12.

Metal foil strip 46 is welded to the outer end of the lead-in wire 23and a resistor 26 is welded at one end to lead-in wire 24 and at theother end to the arc tube harness. The resistor may have a value of, forexample, 40,000 ohms and serves to limit current to auxiliary electrode18 during normal starting of the lamp. Metal foil strip 46 is weldeddirectly to stiff lead-in wire 7. Metal foil strip 35 is welded at oneend to a piece of molybdenum foil sealed in the arc tube 12 which inturn is welded to main electrode 13 and at the other end to the harness.The pinched or flattened end portions of the arc tube 12 form a wideseal using substantially the full diameter of the tube 12 and are madeby flattening or compressing the end of the are tube 12 while it isheated. In addition to the halide and the metal which changes theemission color as described before, the arc tube 12 is provided with afilling of an ionizable media such as mercury in suflicient quantity tobe completely vaporized when pressure-is developed in the order of /z toseveral atmospheres during operation of the lamp. In addition, a smallquantity of a rare gas such as argon, at a normal pressure of 25 mm. ofmercury is introduced to facilitate starting.

The U- shaped wire, internal supporting assembly or are tube harnessserves to maintain the position of the arc tube 12 substantially coaxialwithin the envelope 2. To support the are tube 12 within the envelope 2,the stiff lead-in wire 6 is welded to the base 53 of the harness.Because stilt lead-in wires 6 and 7 are maintained at differentelectrical potentials, they must be insulated from each other, togetherwith all members electrically associated with each of them. A rod 59bridges the free ends of the U-shaped support wire 54 and is fixedlyattached theretoto impart stability to the structure. The free ends ofthe U-shaped support wire 54 are also provided with a pair of resilientmetal leaf springs 60, frictionally engaging the upper tubular portionof the lamp envelope 2.

Supported upon the legs of the U-shaped harness 54 are a pair ofreflective plates 61 and 62, the purpose of which is to support a glasssleeve 55, entrap heat generated by the arc tube 12 and raise thetemperature. Preferably these plates 61 and 62 are attached to theharness 54 by spot welding a pair of braces 65 to the legs of the frame.Of course, the braces can be eliminated and the plates welded directlyto the leg 54 if the sleeve 55 is not too heavy.

The sleeve 55 is resiliently supported upon tabs 66 which extendoutwardly from the periphery of the plates 61 and 62 and are bentinwardly toward the center. The tabs 66 are desirably bent so that asmall gap will be left between the plates 61 and 62 and the ends ofsleeve 55 when the latter is mounted. This arrangement provides someventiliation about the arc tube. In addition, the tab-type mountingprovides resiliency and allows the glass sleeve 55 to move slightly ifthe lamp is shaken thereby avoiding rigidity which could cause damage.

Preferably the sleeve 55 is made of quartz glass which is transmissiveto ultraviolet light. Other types which may be used, however, arevanadium loaded glass which will transmit visible and infrared butabsorb ultraviolet light. Furthermore, dichroic coatings can be usedwhich absorb infrared radiation but transmit other light.

The are tube 12 also is supported by the reflective plates 62 and 63.With reference to the lower plate 61, the end of the arc tube 12 extendsthrough an aperture in the plate and is laterally supported by mutuallyopposed flanges 67 (only one of which is shown). The ends of the flange67 are crimped and usually spot welded together to fit tightly aroundthe press seal. The are tube 12 is supported at the upper end by theplate 62 in a similar manner.

Referring now to FIGURE 2, the perspective view of the assembly is shownin more enlarged detail. As shown, the end of the arc tube 12 extendsupwardly through an apertured plate 62, the aperture being formed by'stamped out sections which are bent to form mutually opposed flanges.The ends of the flanges 68 are crimped together to make the fitting abuttightly against the press seal portion of the arc tube and prevent itfrom moving.

Upwardly extending as stamped out sections of the plate 62 are braces 65which are attached to the legs 54 of the harness by spot welding.Downwardly depending from the periphery of the plate 62 are tabs 66which hold glass sleeve 55 and prevent it from moving while concurrentlyproviding a ventilation port through which the gas in the outer bulbousenvelope can circulate.

Referring now to FIGURE 3, a different type of arc tube is shown. In thefigure, the arc tube 101 is generally made of quartz although many othertypes of highmelting, transparent materials such as alumina glass orVycor may be used. The press seals 103 and 105 are formed in aconventional manner and according to conventional techniques by heatinga glass tube to its softening point and then press sealing the sidestogether upon a series of lead-in wires and molybdenum foil sectionswhich extend through the seal from the outside of the tube to theinside. Attached to the molybdenum foil sections and the inside of thearc tube are the cathodes which are similar to those conventionally usedin the art. These cathodes comprise tungsten or molybdenum core portions111 and 113 upon which wire helixes 102 and 104 can be mounted.

Such are tubes can have heater coils 115 and 112 disposed upon lead-inwires 119 and- 117 which, extend through the press seals 103 and 105 toexternal circuitry.

welded directly to the molybdenum foil sections 106 and 108. The heatercoils extend from inside of the seal to a position surrounding the coreportions 113 and 111 for a few turns at which point they are screwedonto the helixes 102 and 104 so that the ends of the wires of the heatercoils are substantially at the same points as the ends of the wirehelixes. It is generally found desirable to wrap three or four turns ofthe heater coil about the core portions 111 and 113, however they shouldbe spaced and hence, electrically insulated therefrom. It has been foundthat for 400 watt lamps, a 0.008 to 0.0011 inch wire should be used forthe heater coils 115 and 127 although these diameters may be variedbetween about 0.006 to 0.015 inch depending upon the size of the lamp.

A starting probe 123 can be positioned through the press seal 105 toextend into the interior of the arc tube and facilitate initiation ofthe arc as is conventional with high pressure electric dischargedevices. The probe 123 may be positioned anywhere in the arc tube solong as the ends are reasonably close to the respective cathodes. Hencethey may even extend through the side wall of the arc tube 101 ratherthan through the press seal 105. A position in the side wall isfrequently desirable because electrolysis between the bases of theprobes and the cathodes may be markedly reduced, it being almostimpossible for electrolytic action to take place at such disto the powersupply and heater coil 115 is connected to the other side of the powersupply through lead-in wire 136. Frequently a circuit breaker (notshown) is disposed between probe lead-in line 137 and cathode leadinline 138 to short out the probe circuit and prevent electrolysis when anarc is formed in the arc tube 101.

A further description of the circuit is given in the copendingapplication of John F. Waymouth entitled Electric Discharge Device,Serial No. 302,656, filed August 8, 1963 and assigned to the sameassignee as the instant application.

Mounted upon the harness legs are upper and lower reflective plate 139and 140. Noting upper plate 139, a brace 141 is spot welded to leg 133and is disposed with a slip-fit, collar-type insulator 142 about harnessleg 143. Lower plate is spot welded through brace 144 to harness leg 143and is disposed with a slip-fit, collar type insulation 145 upon harnessleg 133. The insulators 143 and 145 may be prepared of any suitableinsulating material such as a ceramic.

Insulation of the plates from the legs of the harness is necessarybecause each leg carries opposite sidesof the power line. Additionally,it is necessary to insulate the legs from each other at the top of theframe by providing an insulator tube 148 which is disposed upon inwardlyextending rods 146 and 147, the inward ends of the rods beingsufliciently spaced from each other to prevent a short circuit.

The disposition of the arc tube within the aperture formed by crimpedflanges 149 and 150 is similar to that shown and described withreference to FIGURES 1 and 2. Furthermore the support of the glasssleeve 153 upon the inwardly extending tabs 152 is similar to thatdescribed previously.

It is apparent that modifications and changes can be made within thespirit and scope of the instant invention but it is my intention,however, to be limited only by the scope of the appended claims.

As my invention I claim:

1. A high pressure electric discharge device comprising: an arc tubecontaining a halide and an are forming metal disposed within an outerbulbous envelope, said are tube having press seals at either endthereof; an arc tube harness disposed within said envelope; a pair ofplates disposed upon said harness; a glass sleeve disposed between saidplates and about said are tube; means forming an aperture in each ofsaid plates, said press-seals extending through said aperture; a seriesof tabs disposed upon each of said plates projecting inwardly into theinterior of said sleeve, said sleeve resting upon said tabs and beingsupported thereby to form a heat entrapping chamber about said arc tubeand between said plates.

2. The device according to claim 1 wherein the ends of said sleeve arespaced from said plates.

3. A high pressure electric discharge device comprising: an arc tubecontaining a halide and an are forming metal disposed within an outerbulbous envelope, said are tube having press-seals at either endthereof; an arc tube harness disposed wihin said envelope; a pair ofplates disposed upon said harness; a pair of flanges stamped from eachof said plates and forming an aperture therein; a glass sleeve disposedbetween said plates and about said arc tube; the press seals of said aretube ex tending through said plates and being secured by said flanges; aseries of tabs disposed upon each of said plates and projecting inwardlyinto the interior of said sleeve, said sleeve resting upon said tabs andbeing supported thereby to form a heat entrapping chamber about said aretube and between said plates.

4. The device according to claim 3 wherein the ends of said sleeve arespaced from said plates.

References Cited by the Examiner UNITED STATES PATENTS 2,841,733 7/1958Hodge '313220 X 2,972,693 2/ 1961 Rosenberg 313-17 X 3,085,171 4/1963Srnialek 313-25 FOREIGN PATENTS 737,913 10/ 1955 Great Britain.

20 GEORGE N. WESTBY, Primary Examiner.

S. SCHLOSSER, Assistant Examiner.

1. A HIGH PRESSURE ELECTRIC DISCHARGE DEVICE COMPRISING: AN ARC TUBECONTAINING A HALIDE AND AN ARC FORMING METAL DISPOSED WITHIN AN OUTERBULBOUS ENVELOPE, SAID ARC TUBE HAVING PRESS SEALS AT EITHER ENDTHEREOF; AN ARC TUBE HARNESS DISPOSED WITHIN SAID ENVELOPE; A PAIR OFPLATES DISPOSED UPON SAID HARDNESS; A GLASS SLEEVE DISPOSED BETWEEN SAIDPLATES AND ABOUT SAID ARC TUBE; MEANS FORMING AN APERTURE IN EACH OFSAID PLATES, SAID PRESS-SEALS EXTENDING THROUGH SAID APERTURE; A SERIESOF TABS DISPOSED UPON EACH OF SAID PLATES PROJECTING INWARDLY INTO THEINTERIOR OF SAID SLEEVE, SAID SLEEVE RESTING UPON SAID TABS AND BEINGSUPPORTED THEREBY TO FORM A HEAT ENTRAPPING CHAMBER ABOUT SAID ARC TUBEAND BETWEEN SAID PLATES.